TRV's won't shut off completely

12 Feb 2017
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United Kingdom
Hi all, i've just finished fitting a couple of new column rads and decided to fit all new Bently traditional TRV's downstairs to complement them.
Now the system is all up and running, fully balanced and all the air bleed out. I've noticed that a couple of the largest rads which are in room's we hardly use won't shut off completely. I checked the temperature in the room before switching the heating on with a room thermometer and a handheld digital thermometer on the actual TRV and they both show around 15C despite this after about 10 minuets of the central heating being on the radiators are red hot to touch. I spoke to the manufacturer and they told me to check they are on the flow side of the rad, despite the instructions saying they can be on either! I've checked and 3 rads are on the flow side and 3 are on the return (mainly due to the other side of the rad being partly obscured by furniture) I can swap all the pipe work around under the floor before it's brought down into the room to sort this out but i'm not convinced this will solve the problem as the 3 rads with them fitted on the flow side are still heating up when shut off. I thought TRV's are meant to save money, but at the moment i'm heating rooms which are not being used! Does anyone have any ideas before i drain the system down and remove the valve and try and get my money back.
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1) Take the heads off and try the decorators cap to check if the valve does close completely.

2) If it does then check that the actuator heads are correctly fitted
unfortunately they don't come with decorators cap's. I'm not sure if i can get the the head off it looks to be a single piece
unfortunately they don't come with decorators cap's. I'm not sure if i can get the the head off it looks to be a single piece
You can buy a decorators cap for 89p, so the top must come off. Give the supplier a call. I think they have cheek to charge for the decorators cap for a valve costing £55. Honeywell sent me eight for nothing.
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Sorry brain freeze moment, the tops do come off i've checked and the pins move up and down freely and the actuator heads move down inside when you wind it down. I spoke to the manufacture and they told me they no longer do the decorators cap for those valves the new style has a different thread!
I should have stuck with a well known brand like Honeywell, but i assumed that a TRV wasn't that complicated and couldn't be messed up that badly by a Chinese manufacturer? you know what they say assumptions are the mother of all F*** up's ! Looks like i'm going to have to change back to the plain old Honeywell or Pegler Terrier that have proved faultless for many years in the past, just a shame i spent over £300 on 6 of the buggers!:cry: well at least they looked nice for a while
Make sure the head is set to Max before trying to refit it. If you don't, it may not fit correctly due to the strength of the spring in the head.

You say that the system has been "fully balanced". How far open are the lockshield valves (max and min)?
Your not on your own, my wife has been complaining since we moved into the house her bedroom was too hot in the main, but also some times too cold, so Honeywell valves were old so decided to change heads, only then to find not switching fully off, what I don't know is if due to bit of muck, or faulty valve or seat within the valve, however also realised if the valve has been static for years it may need to work a bit and bed in, so I have set to a working range to see if they bed in.

In my case whole idea was to remotely control the valve, radiator not easy to reach, however if manually altering valve, why don't you turn off with lock shield valve? Also what is the minimum temperature, I know with Honeywell they say if the room cools below a set level they can open even if set to off, think for memory 6°C but could be wrong.

I looked at my boilers instructions and see there is a by-pass valve inside the boiler, and there is also one above the boiler, so people who installed it must have not realised there was one built into boiler, clearly reverse could happen or the by-pass valve maybe stuck.
The radiator furthest from the boiler, also the largest, has the lockshield fully open. This is one of the 3 which is in a room we only use occasionally. The other's are about 1/3 to 1/4 open. And the one in the main bedroom which is quite close to the boiler main feed and return, in fact i think it's the 1st tee off after the 3 port valve. It's also a very large rad and is only open about 1/8th of a turn, with the TRV fully open it get's warm quite quick but this time of year we don't want the bedroom at 30°C all day, hence the TRV which we only open up a bit before we go to bed just to take the chill off. I did have it all recorded on a balancing sheet which i can find at the moment. i'll upload if i find it.
when you say bypass do you mean a differential bypass valve? i've got one fitted in on a branch that tee's off between the pump and the 3 port and feeds just a towel rail in the bathroom, that way the towels are dried when ever the boiler comes on so a lot in the winter and just for 20 mins in the summer which is fine.
The lower range of the BiWorld Bentley valve setting is quite limited. 12 degrees is as low as it goes.

Most TRV's will go lower than this and just provide frost protection.

If the valve is set to the minimum of 12 degrees and the room temperature is at 15 degrees, then it should really be closed. My experience though, is that whilst TRV's are usually quite good at maintaining a room temperature, their dials are not particularly accurate, I have all my main rooms at 19 degrees, but in reality whilst the valves I have (Drayton) do this admirably, they are actually at different settings in the different rooms to achieve the same end temperature.

Perhaps yours will close off fully when the room temperature rises a degree or two more.
Ok thanks for the advise everyone. My next question is can anyone recommend (from experience of having them installed) any traditional looking TRV's that actually have a lower frost setting that will just keep the room above freezing and not heated to 12°C.
If the energy saving trust is to be believed just lowering the room temp by 1°C can save £75 a year so keeping it at 12°C instead of just above freezing say 2°C, that 10°C difference is a potential saving of £750 a year. I know it won't be as much as that in reality, but we have a very cold house and heating rooms that don't need to be is just crazy. When we first moved in our 1st months gas bill was £860! which worked out to be over £6000 a year :eek:

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